Microwave generator



Aug. 19, 1952 F. LUDI 2,607,905

MICROWAVE GENERATOR Filed July 7, 1948 2 SHEETSSHEET 1 Aug. 19, 1952 F.LUDI MICROWAVE GENERATOR Filed July 7, 1948 2 SHEETS-SHEET 2 PatentedAug. 19, 1952 MICROWAVE GENERATOR.

Fritz. Liidi, Zurich; Switzerland, assignor to PatelholdPatentverwertungs- Holding A.-G., Glarus, Switzerland & Elektro- 1Application 11. w, 1948, Serial No. 37,448 In Switzerland August 16,1947 This invention relates generally to devices for generatingultra-high frequency electrical oscillations, i. e. in the centimeterrange, and more particularly to those of the typein which electronsemitted radially from an elongated cathode transfer energy to an annularhollow resonae tor arranged concentric about the axis of the cathode;The resonator has annular end walls bounded in a, radial direction byouter and inner cylindrical walls, and the inner wallis .constituted bya cylindrical array of spaced anode segments, adjacent segmentsin thearray. being secured to opposite end Walls suchthat alter nating,potentials are developed between adjacently positioned segments as the.resonator oscillates. Through the combined actions of a constantradialelectric field established between the cathode and the array ofanode segments byan applied potential and a unidirectional magneticfield established axially, the electrons-leaving the cathode are-causedto. travel in cycloidal paths'and form into bundles which then give upenergy, originatingirom the constant electric field to the alternatingfield of the cavity resonator to maintain the latter in a stateoioscillation at a. constant frequency which is determined solely by itsdimensions and the capacity between the anode segments. The appearanceof this type of generator-which is. de-. scribed in further detailin myco-pending United States application, Ser. No. 78,533; filed March9,1948, and also in. anarticle prepared by me which-appeared in-Helv.Phys. Acta, vol. XIII Fasc. Sext (1940-), is somewhat like that of analternating current machine.- The ,cavity reso: nator determining thefrequency along with the anode segments resembles a. stator while themotion of the electron bundles corresponds to the movement of the.rotor.

While this type of micro-wave generator has been found to. producegenerally satisfactory results, it does, however, have oneoperatingdisadvantage thatste'ms from the so far unavoidable. coupling betweenthe high. frequency magnetic field. within the resonator and the cathodewhich it encloses. l

such. coupling causes a loss of energy; because of; the high frequencycurrents induoedin the cathode that are free to flow offon the cathodeinput line,- and makes it possible, through the coupling, for the highfrequency field to. besdisw turbed by extraneous fields and: chargesthat under optimum operating conditions should. be enti'relyexclud'ed.,The general object of: the present invention is. to. overcome the abovementioned undesirable operating characteristic by eliminating thecoupling between thehigh frequency magnetic field ofthe cavity and thecathode and specificallyby providing at least two cavity resonatorsenclosing the cathode and coupling these .resonators in a manner suchthat the instantaneous Sllmzof the high frequency fields simultaneouslyaffecting the cathode is always equal to zero;

By. sodoing, the undesirable high frequency currents are 'nolonger"induced. in. the, cathode line, the resonators: are completely isolatedfrom all harmful extraneous effects and one also is able to. enjoy theadditionalv advantageof a much broader latitude in designing the cathodestructureper. ser since research has shown that large surfaced cathodesaredesirable in the interest of increasing. the efficiency of thegenerator, the ratio of" the anode to the cathode diameters beingparticularly important. V I

Another specific ObjECtrlS. toprovide an improvedmicro-wave generator.having a pair of intercoupled' cavity resonators, the high frequencyfields 'ofwhichare displaced 180 apart in phase. 1

Yet-:another. specific object is to providean improved. micro-wavegenerator having three associatedcavity. resonators for usein producingthree phase oscillations, the high frequency; osci-llationsoitheseveralphases .beinajintercoupled so .aszto be displacedlZO-tapart in phase.

"The foregoing as well. as other objects and accompanying drawings. Fig.1 is..a perspective view illustrating one embodiment of the invention.in which thegenerator is'provided with a Pair. of adjacentinterconnected cavity resonators, the oscillations of which are spaced180 apart in phase the usualmagnetic structure by which a;unidirectional; magnetic field -is-.established parallel: to .the. axisof the cathode, has been omitted forthe sake of simplicity. fig. 2 isaverticalsection; taken along the axis. of the. oath.-

r highfrequency oscillatory circuit produced by the"generatorsillustrated in Figs. 1 and'Z. Fig,

tors through the envelope surrounding the generator elements.

Referring now to Fig. l, the improvedv high frequency generator is seento include the usual cathode I, heated indirectly by filament la,

having a relatively large surface for the emis sion of electrons andwhich lies along the axisv of a pair of annular, adjacently positioned,cavity type resonators legended A and B. The two resonators are combinedin a single hollow cylindrical conductive structure made up from anouter cylindrical wall 3 of conductive material extending longitudinallyof the cathode, annular conductive end walls 4 and 5 extendingtransversely of the cathode, a third transverse annular conductive wall6' placed intermediate the end walls 4, 5,-and an inner cylindrical wallparallel with theouter wall 3. This inner wall is comprised of acylindrical'array of spaced anode segments 1 extending parallel to thecathode inwardly from end wall 4 to a point just short of intermediatewall 6, a similar array of anode segments 8 extending inwardly from endwall 5 and which are aligned with the anode segments 'L-and a thirdcylindrical array of spaced anode segments 9,10 carried by theintermediate wall 5 and which extend'respectively in opposite directionstherefrom. Anode segments 9, In likewise lie parallel to the cathodeaxis in thespaces between anode segments 1, 8 and terminate just shortof the end wallsal, 5.

Resonator A is thus constituted by the;cavity defined by outer wall 3,anode segments 1, 9 and transverse Walls 4, 6; and resonator B isconstituted by the cavity defined by outer Wall 3', an- I ode segments8, l6 and transverse walls..5, 6.

- The capacity component of each resonator con-v sists principally ofthe inter-leaved segmentscarrie'd -by the end and intermediate walls,respectively and these segments during operation are at any-instant ofopposite polarity. :LThUSfOI' example in resonator A, at the instantthat the anode segments 7 secured to end wall are charged positive, theanode segments 9 secured to intermediate wall 6 will be chargednegative, and vice versa, as the resonator circuit oscillates.Resonators A and B and the cathode l are all enclosed within anevacuated envelope II; a post '12 beaded into the lower end of theenvelope is usedto support the resonator structure; filament la. and thesurroundin cathode l are anchored in place by rigid lead-in conductorsl3, M for the filament current which are also beaded into the lower endof the envelope; and parallelarranged lead-off conductors 15, I6, I!forthe high fre-f duency oscillations produced by the generator extendthrough bead type seals at theupper end of envelope I l in a directionperpendicular 'to the cathode axis, it being noted that conductor 16 isconnected directly to the outer 'wall 3 at the common intermediate wall6 separating the two resonators A and B while conductors and I! passthrough slots l8, IS in outer wall- 3 well into the interior of theresonators A and B, re-. spectively, and there are turnedthrough 90" soas to present short, co-axially aligned coupling i. e. energy extractingsections l5a, Ila extending towards each other in a direction parallelto the cathode axis and which terminate at the intermediate wall 6 andare electrically connected to the latter at the junction point.

The construction of the ultra-high frequency generator shown in Figs. 2and 3 is substantially the same as the one shown in Fig. 1 and for readycomparison between the two structures, like reference numerals but withprimes added thereto have been used to designate like parts in the twostructures. In addition, the pole pieces 22, 23 of a generally C-shapedmagnet are shown in Fig. 2

at opposite ends of the cathode l on which are wound field coils 2d, 25that are energized from a sourceof' direct current, not illustrated, toestablish a unidirectional magnetic flux parallel to the cathode axiswhich is essential to the generator. As previously explained, thecorresponding field structure associated with Fig. 1 has been omitted inthe interest of simplifying the disclosure.

As can be readily observed by a comparison of Figs. 1 and 3, the onlydifference between-the generator constructions in Figs. 1 and 2 lies inthe manner in which theanode segments associated with the end walls ofthe resonators are arranged. In Fig. 1, two galvanically' separateand'aligned arrays of segments 1 and 8 are utilized whereas in Fig, 3,the aligned segments in each array are seen to be continuous between thetWo'end walls 4, 5, and arcuate notches 26 are cut into the intermediateplate'6 to prevent cont'actbetween the latter and these segments. Thusalthough the anode segments are actually one continuous body ofmaterial, separate legends "l-,-8 ---have-nevertheless been used thereonto designate-the anode portions associated respectively with resonatorsA and B'. I

It will now be apparent from what has been said that the generatorsshown respectively in Fig; Land Figs. 2, 3 each provide dual, highfrequency oscillatory circuits, one including resonator A and the otherresonator B, with the cathode I common to both circuits. Consideredseparately, each of the resonators operates in accordance with thepreviously explained principles." 3

stated at the outset; the principal object of this i'nvention is 'tomore effectively isolate th cavity resonator component of'the generatorfrom all extraneous charges or fields that might exert a disturbinginfluence on the high frequency oscillations generated because of theinductive cou- 'pling between the high frequency magnetic field andcathode. The desired result is obtained in Fig. l and Figs. 2, 3 byproviding dual resonators and arranging these such that the respectivephases of the high frequency fields are stage gered by".1 That is tosay, the field in 'on resonatoris always opposite in direction to thatintheother resonator, such condition being illustrated schematicallyiri"Fig. ,2 by the usual 65 and'Q direction symbols. Under these canal--tions, the induction eifects of the two 'high'fre .terunderstanding ofthe. nature of th'ecoup'ling to beapplied, reference should be made toFig. 'ithat-shows schematically two oscillatory circuitsoa and b-connected'in' parallel and oscillating in opposite phaseasindicated bythe directional arrows. oscillatory circuit a corresponds to resonator Aand oscillatory-circuit b to resonator B. Condenser-plates 3-0*ofcircuit Ia'repre sent the capacitance of anode segments 1, '9 ofresonator A; condenser plates 3'l= of circuit b represent'thecapacitance ofanode segments 8, I oiFre'sonator'B; coil 32 representsthe inductance of circuit aconstituted by end walls 4, 6 and that halfof. outer wall 3 included therebetween; and coil 33' the inductanceofcircuit. lr constituted by end walls- 5, I6. and the. other half ofouter wall 'Sincludedtherebetween.

'The'coupling between points 34 and 35 of the two circuitsin thegenerator'shown in Fig; l, and also in. the modified .c'onstructi'onshown in Figs. 2; 3is established by the conductive intermediate wallfi'which iscommon'to both resonators. The coupling between points 36 and31 of the two oscillatory circuits is, however... established by.difierent means in the two constructions in Fig. 1,, suchcouplingis'produced by direct connection of: the symmetrically arranged'couplingloops l a, We. of the two lead-oil conductors l5, 1''! whichterminate at the conductive intermediate wall ii;v

- while in the Fig. 2 construction, such coupling is established byvirtue. of'thefact that correspond- Fig. 5 illustratesstilla'thilid'manner of, forming the connection betweenpoints. 3.6,. 3'! ofthe twooscillatory circuits. at. andb for .a. generator having theresonator structure. of Fig. .1. Here it is. seen that the necessaryinterconnection is established by a. conductor 38 having acouplinglo.op..38a disposed. within resonator A" and a similar. coupling.100pfl38 within resonator .B" but looped in the opposite direction, theterminalends of the conductor being connected to the intermediatetransverse wall 6", and being passed through an opening 39inv thelatter.

It is easily seen that only a state. of oscillation can be formed whichinduces like-directed currents in the two looped portions of conductor38, as shown bythedlrectionarrows. This is possible, however, only whenthe two fields are in opposite phase,..as. shown, the purpose of; thewire loop '38 being thusfilled. I .Fig. 6 illustrates in a somewhatdiagrammatic form a further modification utilizing threeresonatorsintercoupled 'in such. manner that their respective highfrequency fleldsare staggered in phase by 1 20 electrical degrees. Igenerator is especially suited for producing three phase high frequencyoscillations. Basically, this form of the invention is the same as thatshown in Fig. 1 and, in the interest of simplifying the drawings, onlythose anode segments lying in the plane of the cathode axis :r--.'z:have been illustrated, and the cathode itself has also been excluded. Aswith the other embodiments, the resonator structure is comprised of anouter cylindrical wall 40, parallel with the cathode axis, annular endwalls 4|, 42 transverse to the cathode axis and a pair of annulartransverse walls 43, 44 intermediate the end walls so located as todivide the interior into three, like dimensioned resonators C, D and E.Circular arrays of anode seg- This form of ments 45, 46 extend inwardlyfrom end walls 4|,

6 v ments 41-, 4'8 extend in both directionsl from the intermediatewalls 43', 44; respectively, soas 'to lie in the spaces between theanode segmentsiflg Coupling loops 5 I, 5 2 and'53 extend respectivelyinto thethreeresonators C, 'D and El-for extract; ing high frequencyenergy from the generator;

and these lead'via concentric lead-ofi waveguir'i'esv 54, 55, 56 toastar connected three phase load apparatus-indicated diagrammatically byth'e rece tanglesil. Y

Inorder'that the three resonators C, D men shall have the necessaryphase displacement of coupling connections '58, 59 must be- .vi'ded."Connections 58, seen tobe-of the capacity type couples conductors "5'4and 55-; and conneee tion- 59, also of the capacity type-couples: coneiductors'ifi-and 56. By correct choice of "thedistance ."yand 2 betweenthe outer wall and coupling connection 58-, 59 respectively, whichin'the simplest manner is determined imperica-lly'. the desired "phasedisplacement between' resonators C', D. E can be effected withoutdi'iliculty; so that, for example, resonator D oscillates, with a phasedisplacement of 120 in relation to reso nator Cyandf resonator E with aphase displacement of 240" in relationto resonator C. In this. way, thesum of the inducing effects of the high frequency magnetic field's ofallthree resonators.

on the cathode is equal to zero; and radiation of high frequency energythrough the catho'de made impossible;

'In't'he dual resonator generator construction shown in Fig. 1, it"i'sof advantage to maketh'e connection between the high frequency conducptors inside of the envelope so that onlytwo conductors need be.carried'out' of the envelope'ior coupling out the high frequencyenergy. Such an arrangement is illustrated. in Fig.1? where it. will beseen that lead-off conductor I5? isxconnected 'bya bridge 60' toconductor 11"" within the envelope 'II"', and hence only conductors. IT'and 16"" are then necessary for leading. out the high frequency energy;The two cathode lead-ins l3"" l4 are then preferably led; out of theenvelope l'l'" on the. same side 'asconductors' IB, l1""., the fourconductors. l'ieingarranged in the form of a cross.

I claim:

.1. Amicro-wave generator comprising a cathode; a..plurality of likeannular hollow resonators-surrounding said cathode and located inside-by-side'relation along the cathode axis and concentrictherewith,..each of said resonators including, annular. end walls andbounded in-Ja radial direction by an outer cylindrical wail and aninner'wall constituted by a cylindrical array of Iinterfi'tti'ng anode."segments. terminating, in alternation on said end walls; means adjacentsaid resonators for establishing a unidirectional magnetic field withinthe space defined by said inner wall of each resonator and parallel tothe common axis thereof; means symmetrically arranged in the respectiveresonators for extracting high frequency energy therefrom; and meansintercoupling said resonators together and so constructed and arrangedthat the inv ductive effect of the high frequency magnetic fieldsproduced respectively by the resonators with respect to the cathode iszero.

2. A micro-wave generator as defined in claim 1, wherein said meansintercoupling said resonators includes said symmetrically arranged meansfor extracting high frequency energy from the respective resonators.

3.,A.; micro-wave generator comprising an evacuated envelope housing acathode; an annular resonator structure disposed concentrically aboutsaid cathode, said resonator structure comprising annular endwalls, anouter cylindrical wall extending between said end walls, an intermediateannular wall parallel with said end walls and an inner cylindrical wallconstituted by a cylindrical array of interfitting anode segmentsterminating in alternation on said end and intermediate walls, theannular space defined between one of said end and intermediate walls andthe inner and outer wall section therebetween constituting oneresonator, and the similar space defined by said intermediate wall andthe other end wall and by the sections of the inner and outer wallstherebetween constituting a second resonator; means adjacent saidresonators for'establishing a unidirectional magnetic field within thespace defined by the inner wall of. each resonator and parallel to thecommon axis thereof; lead-off meanscoupled to each resonator forextracting high frequency energy therefrom; and means including saidintermediate wall that is common to both resonatorscoupling the lattertogether in parallel and so constructed and arranged that the inductiveeffect of th high frequency magnetic fields pro- [duced respectively bytheresonators with respect 'to said cathode is zero.

4; A micro-wave generator as defined in claim 3 wherein said couplingmeans comprises means coupling together the high frequency lead-off.means of the respective resonators.

'5. Amicro-wave generator as defined in claim 3'wherein said couplingmeans comprises means interconnecting the high, frequency lead-olf- '3wherein said coupling means comprises a coupling loop extending throughan aperture in said intermediate wall into both resonators and whichsurrounds the respective high frequency fields of the resonators ininverse sense.

7. A micro-wave generator comprising a cathode; three annular hollowresonators disposed concentrically about said cathode in side-by-siderelation, each of said resonators including annular' end walls andbounded in a radial direction by an outer cylindrical wall and an innerwall constituted by a cylindrical array of interf'fitting anode segmentsterminating in alternation on said end walls; means adjacent saidresonators for establishing a' unidirectional magnetic field within thespace defined by the said ne l, p each ire na p l.a dy a a l l i m naxis p :13 10 m? metrically positioned .with respect to the ree spectiveresonator "for extractingv high frequency energy therefrom; and meansintercoupling said resonators together and so constructed and arrangedthatthe respective high frequency magnetic fields produced .by saidresonators are apart in phase.v f I 8. A micro-wave generator as definedin claim 7 wherein said intercoupling means includes capacity typeconnections extending between said lead-off means. v vI 9. ,A micro-wavegeneratorcomprisinga cathode; an annular hollow resonator structuredisposed concentrically about said cathode; said resonator structurecomprising end walls, an outer cylindrical wall connecting said endwalls, a pair of spaced annular walls arranged parallel with said endwalls and intermediate thereof, and an inner wall constituted by acylindrical array of interfitting anode segments terminatingin'alternation on said end and'intermediate walls, the annular spacesdefined respectively between said end and intermediate walls and theinner'and' outer wall sectionstherebetween constituting three likeresonators; ineans fadjacent said resonator structure for establishing aunidirectional magnetic field within the space defined by the innerfwallof each resonator and parallel to the common axis thereof; lead-01fmeans cooperative with each resonator for ex.- tracting high frequencyenergy; and means including said intermediate walls intercoupling saidresonator chambers together and so .0011- structed and arranged thatthe, inductive reflect of the high frequencyjmagnetic fieldsproducedrespectively by theresonators with respect to said cathode is'zerofi p'10. A micro-wave generator as defined inclaim 9 wherein the meansintercouplingsaid resonators also includes capacitive type connectionsbetween the said lead-o'fi means cooperative with the severalresonators. 7 I Y FRITZ LUDI.

E ES ITED The following references are of record in the file] of thispatent:

UNITED STATES PATENTS Number Name 3 Date 2,115,521 Fritz l Apr. 26, 19382,128,237 Dallenbach Aug, 30, 1938 2,144,222 Hollm'alln I. Jan 1'7, 19392,233,261 Hollmann "Feb.,25, 1941 2,409,222 Morton "Oct-l5, 19462,463,416 Nordsieck

